1. Field of the Invention
This invention relates to a method of producing substances useful, for instance, as drugs by utilizing genetic engineering techniques, in particular to a method of producing such substances more efficiently as compared with conventional methods. More specifically, this invention relates to a method of producing such substances in vitro or in vivo by making use of a viral DNA. In a further aspect, this invention relates to a method of producing various useful substances efficiently in vivo in silkworms (Bombyx mori) by making use of a nuclear polyhedrosis virus. The invention also relates to vectors and recombinant viral DNAs, which are useful in carrying out the above-mentioned methods, as well as a method of producing the same.
2. Description of the Prior Art
A number of methods have been reported of producing useful substances in Escherichia coli, Bacillus subtilis, Saccharomyces cereviciae, and so forth by using plasmids and the like and taking advantage of recombinant DNA techniques.
There is also a report describing an attempt to produce .beta.-interferon and .beta.-galactosidase in cultured cells (of an established cell line from Spodoptera frugiperda) by using viral DNA (Autographa californica nuclear polyhedrosis virus DNA) after structural gene substitution therein G. E. Smith et al., Molecular and Cellular Biology, 3 (12), 2156-2165 (1983); G. D. Pennock et al., ibid., 4 (3), 399-406 (1984). However, it is a problem that A. californica which is to be used in carrying out this method is a pest existing in nature. Therefore, this method is not satisfactory as a method of producing useful substances. The present inventors conducted investigations in an attempt to provide a more improved method of producing useful substances and have now completed the present invention.